Continuing the broad industry effort to transform Web pages from static content into frames for third-party Web services, Google on Wednesday released a new Web comment and annotation system called Sidewiki as part of its Google Toolbar browser plug-in.

When browsing the Web with Google Toolbar installed, users can post comments through Sidewiki that become associated with specific Web pages and can syndicate those comments through other social media sites like Blogger, Facebook, and Twitter.

Unlike similar comment services, such as Disqus, which Web site owners must install on their Web pages, Sidewiki associates itself with Web sites regardless of site owners' wishes. It can do so because Internet users are free to add or subtract content to, or next to, existing Web pages using browser plug-ins that give third parties control over screen real estate. It's called personalization.

In this regard, Sidewiki recalls the controversial Third Voice annotation service, or other comment and annotation services like ShiftSpace or Reframe It.

Sidewiki allows users to post information in a sidebar that appears next to Web pages. Were Google to run ads in a sidebar next to other people's Web pages without permission, it would most likely be sued. But because it's publishing ostensibly non-commercial commentary, vetted by an editorial quality algorithm, and because the user invites Sidewiki to the party, Google is likely to find fewer obstacles awaiting Sidewiki.

Indeed, in an effort to assure everyone that content providers welcome Sidewiki annotations, Google has provided in its press material several testimonials endorsing the service. Richard Gingras, CEO of Salon Media Group, for example, observes that Sidewiki could help users engage with its news reporting by "furthering the conversation around the issues we cover."

Key to Sidewiki's success will be the utility of its editorial quality algorithm. If it fails to distinguish between insightful comments and self-serving spin, blather, or invective, users are likely shun the service as a source of unnecessary noise.

Google launched a similar service for annotating search results called SearchWiki last November. In June, the company added a way to disable SearchWiki, "after months of requests from its users," as Matt McGee, writing for Search Engine Land, put it.

Google's VP of product management Sundar Pichai and Sidewiki engineering lead Michal Cierniak believe that the company's code can separate the insight from the ignorant yammering. "In developing Sidewiki, we wanted to make sure that you'll see the most relevant entries first," the two said in a blog post. "We worked hard from the beginning to figure out which ones should appear on top and how to best order them. So instead of displaying the most recent entries first, we rank Sidewiki entries using an algorithm that promotes the most useful, high-quality entries."

The ranking system weighs feedback from the person submitting the comment and from other users, past entries by the commenter, and a variety of other quality signals.

Sidewiki is part of Google Toolbar, which is available for Firefox and Internet Explorer. Google says it's working on making the service available for Chrome and possibly other browsers.

Google is also making an API available, so that developers can access Sidewiki data and use it in their own applications or on their own Web pages in a different form.